In general, a pressure vessel has a structure configured to contain a fluid, for example, a liquid, a liquefied gas, a condensable gas, and a combination thereof under pressure. Such a pressure vessel includes pipes and other ducts (hydraulic lines, etc.) which may be used to raise a pressure to transfer a fluid, and structures (rocket motor casings, launch tubes, etc.) exposed to a transient elevated pressure, as well as storage vessels (fuel tanks, portable gas storage tanks, etc.).
Such a pressure vessel has been typically manufactured using a metal. However, a pressure vessel manufactured using a conventional metallic liner has problems in that it is heavy in weight and highly susceptible to corrosion, and also has high manufacturing costs.
To solve the above problems, pressure vessels in which reinforcing fibers such as carbon fibers or glass fibers are wound around or stacked on the outside of a plastic liner have been increasingly used. For example, Korean Unexamined Patent Publication No. 10-1998-701932 titled “Pressure Vessel and Method of Manufacturing the Same,” discloses a pressure vessel including an inner liner having a gas barrier property and a pressure-resistant outer liner installed to cover the inner liner, and the outer liner is formed of FRP including reinforcing fibers and a resin and also has an tensile modulus of 35 GPa or more and a tensile strain at break of 1.5% or more.
A matrix resin is generally impregnated with the reinforcing fibers, and wound around or stacked on a plastic liner. Since the matrix resin serves to transfer stress applied to a pressure vessel to the reinforcing fibers, physical properties of the resin are also an important factor in designing the pressure vessel. In particular, since a pressure vessel for compressed hydrogen gas uses a higher charging/discharging pressure than other pressure vessels, the contraction and expansion of the pressure vessel are high during a charging/discharging cycle, and high heat is generated.
In this case, the matrix resin applied to the pressure vessel for compressed hydrogen gas requires high elongation and a high glass transition temperature. Therefore, there is an increasing demand for a matrix resin satisfying such requirements, a low-viscosity liquid epoxy resin composition including the matrix resin, and a pressure vessel manufactured using the same.